This proposal is directed toward the study of normal color vision, and to the assessment of the color defects which occur in individuals with stationary, hereditary color defects and those which occur in various retinal and choroidal disease states. Psychophysical methods will be used to study heterochromatic sensitivity, color matching, and spectral sensitivity of the cone mechanisms. These studies are designed to reveal the nature of the retinal cone mosaic, including the numbers and types of photoreceptors in observers with normal and abnormal color vision. Psychophysical and electroretinographic techniques will allow basic studies of the short wavelength sensitive (SWS) cone mechanism in color normal individuals and in patients with retinal disease. Studies of temporal modulation sensitivity using heterochromatic modulation photometry will be performed with the aim of separating the effects of radiance, chromaticity and temporal frequency. Retinal densitometry will be used to study cone visual pigment kinetics in color normal and color defective observers and will evaluate the feasibility of studying cone visual pigment kinetics in patients with acquired macular disorders. The development and evaluation of protocols for testing patients with eye disease will be continued. The aim is to develop easily-performed and rapid tests which give specific information concerning visual function in eye disease. In addition to empirical studies, models of normal and abnormal color vision will continue to be developed. The theoretical approach is based in the question: to what extent can established biological or physical phenomena explain the data of color vision? This approach is one which allows us to examine the plausibility of various hypotheses which are not subject to direct experimental evaluation.